1. Technical Field
Example embodiments of the present invention relate to a software-defined networking technology, and more specifically to a method for changing a role over control authorization for a controller in an environment having multiple controllers.
2. Related Art
The networks comprising conventional routers and switches are configured with complex protocols and functions. Since operation methods and user interfaces for them are different according to vendors of apparatuses, it is difficult for network operators and researchers on network technologies to develop new network protocols to be applied to networks, to expand the network, and to make the network apparatuses interwork with each other. In order to overcome the above-described problem, there have been studies on technologies of switches and routers having open-type interface. However, since the network technologies based on the open-type interfaces are expensive as compared with their performances, their commercialization was not achieved easily.
‘OpenFlow’ technology appeared in order to resolve the high cost problem, and provide users and developers with open-type standardized interfaces.
The OpenFlow technology separates a packet forwarding function and a control function of a network switch, and provides a standardized protocol for communicating between the two functions. Therefore, if the OpenFlow technology is used, packet paths may be determined by using software driven in an external control apparatus, and traffic may be controlled more precisely than the conventional technologies.
Open Networking Foundation (ONF) has defined a software defined networking (hereinafter, referred to as ‘SDN’) technology which can enable easier network programming possible based on OpenFlow.
A SDN structure based on OpenFlow comprises a plurality of OpenFlow switches and at least one controller. The OpenFlow switches and the controller may be connected to each other by using the OpenFlow protocol.
In the SDN network based on OpenFlow, a controller may provide flow table information to switches, and the switches may change properties of packets using the provided flow table information, or process the packets by controlling flows of the packets.
A switch may be connected to multiple controllers, and each controller connected to a switch may have at least one of control authorities such as a Master, a Slave, or an Equal. Here, since a controller acting as a master may perform a command function related to traffic control for the switches, it is very important to a switch which controller has a master controller authority.
Meanwhile, in addition to the ONF, various standardization organizations such as an Internet Engineering Task Force (IETF), an European Telecommunication Standards Institute (ETSI), an International Telecommunications Union-Telecommunication (ITU-T), etc. have been progressing standardization on the SDN-based networks.
For example, an Interface to Router System (I2RS) working group of IETF is progressing standardization for providing open-type interfaces to monitor and control conventional network apparatuses from external.
An agent in the I2RS may communicate with multiple clients, and a client may perform an advance procedure with the agent so that the agent assigns a security role to the client. That is, a different role may be assigned to each client, and precedence of commands transmitted from each client to the agent may be determined according to the assigned role. Therefore, a role of the client is also very important in the I2RS. The client of I2RS corresponds to the switch of OpenFlow, and the agent of I2RS corresponds to the controller of OpenFlow.
As described above, in a network environment where multiple controllers are connected to communication apparatus such as a switch or a router, and a master controller controls operations of the communication controller, a role of the controller is very important. Accordingly, the reliability of changing a role (or, control authority) of a controller should be guaranteed.
However, in the conventional method that a controller which newly obtains a right of master reports the role change to a switch unidirectionally, the reliability of changing a role of a controller may not be guaranteed.